There are hundreds of Tx out there to choose from. Be glad that you no longer have the stock Tx because it's either 27Mhz or 72Mhz and both of them have interference issues like crazy. I remember those days and they were horrible. The 2.4Ghz tech that is out now is MUCH better and there are no crystals to change out so that you can your friends can play. Now, you just turn the Tx on, and it finds an open frequency. With the frequency hopping that the new ones have, if your channel starts to get crowded, it will change the channel automatically without you even knowing.
Below is a link to Spektrum's website and their surface Tx's. You can go as cheap as about $150 and the sky is the limit. My Tx that I use for my planes and helis is $430 and it's worth every penny as others will attest to here on teh forum. But for surface, the DX3 and DX4 are great Tx. With what you are doing, the DX3 will work best IMO. The third channel can be used for the reverse that the truck has if it still works.
http://www.horizonhobby.com/browse/productgrid/surine-accesos-10001022
If you can spend the extra cash, get one with Telemetry. You will need to keep an eye on the temp of teh engine and with telemetry, you can do just that. It can also watch teh RPM of the engine and the voltage of the Rx pack in the truck.
As for setup, I have never set one of these up (I was an Airtronics M8 guy when I raced cars and trucks) but I'm sure it's not that difficult at all. Bind the tx to the Rx, set yoru servo positions and end points, and have fun with it.
However, in the link above, you can also purchase the stock 27Mhz Tx that the truck more than likely came with. Yes it's much easier to setup, but I don't trust them much anymore with the new tech.
As stated in the other thread, just post up if you have questions and I will do my best to answer them.